In one of my laptops I use a Compact Flash card for a harddisk. It boots
very fast, programs load much faster. Four GB is more then enough for
the system and the applications.
A good combination in a stationary PC would be some small solid state
harddisk but all the data on a traditional HD. Just keep the swap space
away from the solid state disk, it writes much slower (or use enough ram
to avoid swap at all.
Cheers
herb langhans